1. FIELD OF THE INVENTION
The present invention relates generally to antennas utilized for high frequency radio communication. More specifically, this invention relates to antennas utilized for transmitting and receiving radio frequency signals in the frequency range of 3 to 30 MHz. With even greater particularity, this invention relates to a portable antenna construction for such radio frequency communication providing easy assembly, disassembly, and transportation.
2. PRIOR ART
A number of vertical, dipole, and beam antennas for the 3 to 30 MHz frequency spectrum are currently available. These are generally either single band designs or multi-band designs utilizing traps to electrically shorten or lengthen the antenna for a particular band of frequencies for which the trap resonates. Many such antennas have impedance matching coils to which a transmission line is coupled and which can be tapped to provide a proper impedance match for the transmitter and transmission line. Those antennas designed to operate over a broad spectrum of frequencies are, by definition, low Q devices. They do not sharply resonate at any particular frequency, but rather, maintain a relatively flat frequency response over a broad bandwidth.
Among amateur radio operators, CBers, and short-wave operators, there is a need for an easily assembled and disassembled, relatively high Q antenna operable in the high frequency spectrum. Such an antenna should be easily tunable from frequency to frequency and maintain the ability to match a wide range of transmission feed line impedances.
Dipole antennas for high frequency radio transmission and reception are well-known in the art. The best art known to applicant is contained within the following U.S. Pat. Nos. 3,089,140; 2,875,443; 2,881,430; 3,052,883; 3,737,907.
The U.S. reference Pat. No. 3,089,140 is directed to a multi-band antenna with end mounted loading sections. Trap sections isolate various electrical antenna lengths permitting multi-band operation. However, it fails to provide the center loading coil for matching. Furthermore, it fails to show the overall contour of the antenna of the subject invention. The subject antenna is not a multi-band design and operates on one frequency in the 3-30 MHz spectrum.
The antenna of U.S. reference Pat. No. 2,875,443 is a monopole type vertical having an impedance matching loading coil coupled to ground. It fails to disclose the image antenna of the instant invention when it is operated in the vertical mode.
U.S. reference Pat. No. 2,881,430 discloses a multi-band tuned antenna showing inductive coupling to a low impedance feeder.
U.S. reference Pat. No. 3,052,883 teaches an adjustable dipole antenna, however, it fails to show a center loading coil utilized for matching of the feed line.
U.S. reference Pat. No. 3,737,907 is directed to a multi-band quad and loop antenna, including opposing loading coils. However, it fails to teach matching at the center point, a critical concept to the subject invention.